1. Field of the Invention
The present invention relates to a detector of electromagnetic emissions. It applies in particular to detectors of radars whose objective is to detect, locate and identify the surrounding radar electromagnetic emissions.
2. Discussion of the Background
By contrast with telecommunications signals, intercepted radar emissions consist essentially of trains of pulses which are characteristic of the emitting radar and of its mode of operation. Within this context, radar detectors generally comprise at least three parts which carry out their processing operations sequentially.
A first part carries out acquisition from instantaneous electromagnetic measurements. This acquisition characterizes the pulses received by supplying an estimate of their characteristic parameters, for example the mean frequency, the pulse length, the azimuth, the power level or any modulations that there may be.
A second part carries out the extraction which groups together the pulses relating to each radar emission, separates the various emissions received and characterizes the tracks thus formed, for example by the repetition period and the type of emission mode.
A third part carries out the identification which determines the characteristics of the intercepted radars and of their modes of operation.
The known means of extraction generally employ two essential sub-functions:
a first sub-function performs a sort or pre-processing which groups together the pulses by blocks or classes each presumed to contain the pulses relating to the same emission, PA1 a second sub-function performs an analysis which details the characteristics of the emissions thus extracted.
The sort is done using fast processing carried out for example with microprogrammed hard-wired logic. It pertains to the parameters of each pulse emanating from the acquisition. These parameters are referred to as the primary parameters, for example. The sorting means comprise for example a bank of digital filters, each of which receives all of the pulses emanating from the acquisition and compares the primary parameters of each pulse with brackets characteristic of the filter. A specified radar, defined by a set of brackets pertaining to the primary parameters, is for example associated with each filter. When a pulse is recognized by a filter, it is for example put into a specific memory block associated with this filter.
The number of elementary operations required per second to carry out these sorting operations depends in particular on the pulse density at input and on the number of filters, and hence on the number of radars handled. The computational power required may in particular be as high as a billion elementary operations per second, thereby requiring the development of specific components. These constraints prove to be very expensive and rather incompatible with the cost reductions which are increasingly demanded by the market.